Learn Finnish: Sinun pitää tarkistaa tulot ja menot tänään. - You have to check the income and expenses today.

This is the main rule for obligation verbs like pitää (to have to). The person who has to do the action is always put in the genitive case (the -n form).

Why is the verb pitää and not pidät?

In an obligation sentence, the obligation verb is always locked in the 3rd person singular form (the "he/she/it" form). It never changes to match the person doing the action because the person is already shown by the genitive word sinun.

Is this the same verb as pitää meaning "to like"?

Yes, it is! You can tell them apart by the grammar. When pitää means "to have to", the subject is in the genitive (sinun) and is followed by a basic dictionary verb (tarkistaa). When it means "to like", the subject is in its normal form (sinä) and the thing you like takes a -sta/-stä ending.

What are the base forms of tulot and menot?

The singular base words are tulo (income) and meno (expense). The -t ending makes them plural. Here, they act as the objects of the sentence, meaning they are the things being checked.